SinkholeOdds

Sinkhole risk in Crook County, WY: Pockets of it

Pockets of it

Soluble rock at the surface or under thin cover in part of the county.

On soluble rock
42%
At or near the surface
42%
Buried under cover
0%

What this means before you buy

Check the parcel against your state survey sinkhole map, and ask for an inspection if cracks, depressions or sticking doors show up.

That works out to roughly 1,196 of Crook County's 2,854 square miles on soluble rock, 1,196 of them with the rock at or near the surface. With about 7,775 residents (3 per square mile), much of the land is open, and the mapped rock may sit far from where people actually live. The figures come from 396 map points about 2.7 miles apart, so a pocket smaller than that can be missed or overstated.

Worth reading for this county: why gypsum and salt move faster than limestone, and the signs to look for and how an inspection works.

Counties around Crook County

The nearest county rated sinkhole country is Fall River County, SD, about 108 miles southeast. 1 of the 6 closest counties land in the same band; the ground changes quickly around here.

What Crook County is built on

The largest mapped soluble unit here is the Sundance and Gypsum Spring Formations (sandstone), Middle Jurassic-Upper Jurassic in age, covering about 12% of the county. Next is the Greenhorn Formation and Belle Fourche and Mowry Shale at 11%.

18% of the county sits on gypsum or salt, which dissolves in years rather than millennia. That share matters more than its size suggests.

The county also lies over the Powder River Basin, a deep salt or gypsum basin. Deep beds rarely cause surface collapse on their own, but wells and mining into them have.

Against the rest of Wyoming

Crook County ranks 1 of 23 in Wyoming for soluble rock at the surface, and sits above 85% of US counties on that measure.